EP1752972A1 - Optisches plattenlaufwerk und methode - Google Patents

Optisches plattenlaufwerk und methode Download PDF

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Publication number
EP1752972A1
EP1752972A1 EP05741612A EP05741612A EP1752972A1 EP 1752972 A1 EP1752972 A1 EP 1752972A1 EP 05741612 A EP05741612 A EP 05741612A EP 05741612 A EP05741612 A EP 05741612A EP 1752972 A1 EP1752972 A1 EP 1752972A1
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EP
European Patent Office
Prior art keywords
optical disk
signal
bca
detection signal
period
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Granted
Application number
EP05741612A
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English (en)
French (fr)
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EP1752972A4 (de
EP1752972B1 (de
Inventor
Michinori Matsushita Electric Ind. Co. Ltd. SATO
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Panasonic Corp
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Matsushita Electric Industrial Co Ltd
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Publication of EP1752972A1 publication Critical patent/EP1752972A1/de
Publication of EP1752972A4 publication Critical patent/EP1752972A4/de
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005—Reproducing
    • G11B7/0053—Reproducing non-user data, e.g. wobbled address, prepits, BCA
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head

Definitions

  • the present invention relates to a technique of reading identification information from an optical disk on which bar-code like (stripe-form) identification information is described in some of its area.
  • CD-ROMs/DVD-ROMs which are read-only optical disks
  • CD-Rs/DVD-Rs which are write-once type optical disks to which data can be written only once
  • DVD-RAMs and CD-RWs/DVD-RWs which are rewritable optical disks; and the like are widely known.
  • optical disks which have an area called BCA (Burst Cutting Area).
  • BCA Burst Cutting Area
  • a DVD-RAM or DVD-ROM has a BCA at the innermost peripheral position of the optical disk.
  • a BCA has a bar-code like pattern, which allows identification information for identifying the optical disk to be recorded. This pattern is recorded already at the shipment of the product.
  • An optical disk apparatus reads such identification information before beginning a recording or reading of other information, thus being able to utilize it for the generation of encryption keys, or determine whether playback is permitted or not.
  • FIG. 1 shows an operation procedure of a conventional optical disk playback apparatus.
  • Patent Document 1 discloses an optical disk playback apparatus which operates in accordance with the procedure shown in FIG. 1.
  • step S1 an optical disk is inserted in the optical disk playback apparatus.
  • the apparatus begins optical servo for the optical disk, and at step S3 begins to read address information (ID) from the optical disk.
  • step S4 it moves to a management information position (area) by utilizing the ID, and at step S5 reads management information. Since it is possible to read management information, the position of the management information is determined.
  • ID address information
  • the apparatus Since it is stipulated in the standard that the management information should be disposed at a specific radial position toward the outer periphery from the BCA, the apparatus is able to reach the BCA position by moving a specific distance toward the inner periphery from the position of the management information at step S6. Then, at step S7, the identification information in the BCA can be read.
  • the reason why the BCA is not directly accessed but is accessed by way of the management information area is that no address can be stably determined within the BCA because the identification information in the BCA is added by processing an area of the optical disk. Note that, from any position toward the outer periphery from the BCA, a movement can be made to the management information position without going by way of the BCA.
  • the identification information which is recorded in the BCA can also be read by other techniques.
  • a switch is provided at a designed position of an optical pickup which is taken when radiating light toward the BCA. The position of the BCA can be detected by utilizing this switch, and thus the identification information can be read.
  • the identification information cannot be read.
  • the apparatus must first determine the positon where the management information exits.
  • the stripe pattern in the BCA prevents the apparatus from determining the address (ID) or adjusting optical servo, and therefore management information cannot be read thereafter.
  • optical servo In order to avoid the above situation, optical servo must be begun at a position away from the BCA. However, such an operation would result in the initial laser-irradiated position being away also from the management information position. As a result, movement to the management information position would take time. It would take even more time to arrive at the BCA and read the identification information.
  • An objective of the present invention is to highly precisely determine whether or not a laser-irradiated position is positioned within an identification area (BCA) in which identification information is recorded, and efficiently determine the position of the identification information area.
  • BCA identification area
  • An optical disk apparatus is capable of reading information which is recorded on an optical disk.
  • the optical disk includes: a data area in which main information to be saved is recorded or to be recorded; and an identification area which has optical characteristics different from those of the data area and in which identification information for identifying the optical disk is recorded.
  • the optical disk apparatus includes: an optical pickup for radiating light onto the optical disk and detecting reflected light from the optical disk to generate a light amount signal; a detection section for outputting a detection signal which is in accordance with a change in the signal level of the light amount signal; a pulse signal output section for outputting, each time the detection signal is output, a pulse signal which continues for a second predetermined time; and an area determination section for determining whether an irradiated position of the light is within the identification area or not based on a continuing duration of the pulse signal.
  • the detection section may output the detection signal which indicates that the change in the signal level of the light amount signal has continued for a first predetermined time or longer.
  • the detection section may calculate an average value of the signal level of the light amount signal, and output the detection signal when the level of the light amount signal remains lower than the average value continuously for the first predetermined time or longer.
  • the detection section may output the detection signal when the level of the light amount signal remains lower than a predetermined fixed value continuously for the first predetermined time or longer.
  • the detection section may retain as the fixed value a design value which is lower than a minimum level of the light amount signal obtained during a read of the main information and which is higher than a minimum level of the light amount signal obtained during a read of the identification information.
  • the area determination section may compare the value of the continuing duration against a predetermined threshold value and acquire a result as to whether or not the value is equal to or less than the threshold value.
  • the area determination section may determine that the irradiated position of the light is within the identification area when the value of the continuing duration is equal to or greater than the threshold value, and determine that the irradiated position of the light is not at the identification area when the continuing duration is less than the predetermined threshold value.
  • the area determination section may compare the value of the continuing duration and the predetermined threshold value before one rotation cycle of the optical disk elapses.
  • the identification area of the optical disk may be one of a burst cutting area and a narrow burst cutting area, in which a plurality of stripes are added, the identification information being described in terms of intervals at which the plurality of stripes are recorded, and the pulse signal output section may set the second predetermined time to be equal to or greater than a time which is necessary for reading two adjoining stripes that are recorded at a maximum interval.
  • the detection section may measure changing periods during which the signal level of the light amount signal changes, and output by every third predetermined time a detection signal which specifies a longest period among the changing periods.
  • the pulse signal output section may determine whether or not the longest period has continued for a fourth predetermined time or longer, and if it has, output a pulse signal which continues for the third predetermined time.
  • the present invention by taking advantage of the fact that stripes in an identification area in which identification information is recorded (or specifically, BCA of an optical disk) are periodically provided, it is determined as to whether an irradiated position of light is within an identification area or not. Specifically, since the signal level of a reflected light amount signal periodically changes when light is radiated onto the identification area, a pulse signal which continues for a predetermined time is output every time such a change is detected. Then, based on the continuing duration of the pulse signal, it is determined as to whether the irradiated position of light is within the identification area or not.
  • the present invention since it is not necessary to determine the position of a management information area and perform a servo operation, it is possible to efficiently move to the position of the identification information area and read the identification information. Moreover, since it is unnecessary to provide a switch for detecting the position of the identification information area as in conventional techniques, there are no concerns as to any increase in cost associated with the mounting of a switch.
  • an optical disk apparatus which is capable of recording information onto a DVD-RAM, and playback recorded information therefrom will be described.
  • FIG. 2 show the arrangement of functional blocks of an optical disk apparatus 10 according to the present embodiment.
  • the optical disk apparatus 10 includes a motor 102, an optical pickup 104, an optical pickup transportation mechanism 108, and an optical disk controller 110.
  • FIG. 2 also shows an optical disk 101, note that the optical disk 101 is not a component element of the optical disk apparatus 10 because it is removable from the optical disk apparatus 10.
  • the optical disk apparatus 10 is capable of recording information onto an optical disk (DVD-RAM) 101, and playing back recorded information therefrom.
  • Information which is recorded onto the optical disk 101 means, in the case where a user records a broadcast program onto the optical disk 101, for example, information such as video and audio of the program to be enjoyed.
  • information means the data such as the program, document, or the like.
  • main information such "information" to be recorded onto the optical disk 101 will be referred to as "main information”.
  • FIG. 3(a) shows areas which are provided on the optical disk 101.
  • the optical disk 101 includes: a data area 201 in which main information is recorded; a BCA (Burst Cutting Area) 202 in which identification information concerning the optical disk 101 is recorded; and a management information area 203 in which management information or the like concerning playback or the like of the main information is recorded.
  • BCA Breast Cutting Area
  • the BCA 202 is located at the innermost periphery of the optical disk 101.
  • the BCA 202 is an area ranging between a radius of 22.3 mm (+0.0/-0.4 mm) to a radius of 23.5 mm (+/-0.05 mm) .
  • the BCA 202 includes a bar-code like pattern.
  • This pattern is formed by, for example, radiating intense laser light or the like after forming a track having address information, thus causing substantial partial changes in the optical characteristics (reflectance).
  • various information can be recorded.
  • each individual optical disk may be uniquely identified by changing the pattern from optical disk to optical disk, or a type may be identified by changing the pattern depending on the type of optical disk (disks for rental use or disks to be sold away, etc).
  • portions whose optical characteristics have been changed so as to compose a bar-code like pattern will be referred to as stripes.
  • the management information area 203 is located Near the outer periphery of the BCA 202. Further at the outer peripheral side of the management information area 203, the data area 201 is located. Main information is to be recorded in the data area 201. Management information for controlling the playback of main information is to be recorded in the management information area 203.
  • the motor 102 causes the optical disk 101 to be rotated with a predetermined angular speed or linear speed.
  • the optical pickup 104 radiates laser light onto the optical disk 101, and detects reflected light from the optical disk 101 to generate a light amount signal (RF signal).
  • the optical pickup transportation mechanism 108 (hereinafter referred to as "transportation mechanism 108") moves the optical pickup 104 along a radial direction of the optical disk 101.
  • the optical disk controller 110 which may be a semiconductor chip circuit that is realized as a large-scale integrated circuit (LSI), for example, controls the recording operation of main information, and the playback operation of main information as well as management information and identification information (described later), by the optical disk apparatus 10.
  • the optical disk controller 110 is composed of various functional blocks. Specifically, the optical disk controller 110 includes a revolutions control section 103, a stripe detection section 105, a multivibrator 106, an area determination section 107, and a microcomputer 109.
  • the functions of the respective component elements of the optical disk controller 110 are as follows.
  • the revolutions control section 103 controls the revolutions of the motor 102.
  • the stripe detection section 105 outputs a detection signal which is in accordance with an RF signal that is output from the optical pickup 104. More specifically, if the level of the RF signal changes to or below an average level L of the hitherto RF signal and that state continues for a predetermined period or longer, the stripe detection section 105 outputs a pulse signal (detection signal).
  • the retriggerable one-shot multivibrator 106 (hereinafter referred to as "multivibrator 106") has a function of outputting a pulse signal in response to reception of a signal.
  • multivibrator 106 When receiving a detection signal which is output from the stripe detection section 105, it outputs a pulse signal (BCA detection signal) whose high level continues for a duration B, in response to this signal as a trigger. If a detection signal is again output from the stripe detection section 105 and is input as a trigger to the multivibrator 106 while the multivibrator 106 is outputting a pulse signal, the multivibrator 106 outputs a pulse whose high level continues for the duration B as starting from when this trigger is input.
  • the area determination section 107 compares a continuous high level period (detected period) x of the BCA detection signal in one rotation cycle of the optical disk 101. The area determination section 107 determines that the current irradiated position is within the BCA 202 if the detected period x is longer than the reference period C, and determines that the current irradiated position is within the BCA 202 if the detected period x is shorter than the reference period C.
  • the microcomputer 109 designates a number of revolutions to the revolutions control section 103, and causes the optical disk 101 to rotate. In accordance with the result of area determination by the area determination section 107, the microcomputer 109 controls the transportation mechanism 108. Based on this control, the transportation mechanism 108 moves the optical pickup 104. Based on the laser light which is radiated from the optical pickup 104 and reflected from the optical disk 101, the optical disk apparatus 10 reads and plays back information.
  • the microcomputer 109 adjusts the position of the optical pickup 104 so that laser light is radiated at an outer peripheral position near the BCA 202, e.g., a position corresponding to the management information area 203. Then, the microcomputer 109 causes the area determination section 107 to determine whether this position is within the BCA 202 or not, based on the reflected light. If it is not within the BCA 202, the optical pickup 104 is moved a certain distance toward the inner periphery, and it is further determined whether that position is within the BCA 202 or not. This process is repeated until the result of determination indicates "within the BCA", when laser is finally radiated into the BCA 202.
  • FIG. 3(b) shows the waveform of an RF signal when laser light is radiated onto the BCA 202.
  • FIG. 3(c) shows the waveform of an RF signal when laser light is radiated onto the management information area 203. Either RF signal is generated by the optical pickup 104 based on the reflected light from the BCA 202 and the management information area 203.
  • the voltage level of the RF signal is low at the stripes which are provided in the BCA 202. This is because the stripes have a relatively low reflectance. Note that the interval at which level drops of the RF signal occur corresponds to the interval of the stripes.
  • the interval of the stripes is N times the channel bit length (N: 1, 2, 3 or 4).
  • the RF signal may also drop due to scratches or soil, etc., even when the laser light is radiated onto areas other than the BCA 202, for example. Even in this case, the optical disk apparatus 10 must accurately determine that the drop of the RF signal is not being caused by the stripes. Then, upon determining that the current irradiated position of laser light is within the BCA 202, identification information must be read based on the bar-code like pattern formed by the stripes.
  • the optical disk apparatus 10 determines whether the current laser light-irradiated position is within the BCA 202 or not.
  • the microcomputer 109 issues an instruction to the revolutions control section 103 to cause the optical disk 101 to rotate by setting it at a number of revolutions for reading the identification information in the BCA 202.
  • an instruction is also issued to the transportation mechanism 108 to cause the optical pickup 104 to move its position so that the laser irradiated position will be near the BCA but toward the outer periphery, e.g., within the management information area 203.
  • the optical pickup 104 radiates laser light onto the optical disk 101, and upon receiving reflected light therefrom, generates an RF signal having a level which is in accordance with the received amount of light.
  • FIG. 4(a) shows the waveform of an RF signal.
  • the RF signal has a level-drop portion. This drop corresponds to a single stripe in the BCA 202. However, even outside the BCA 202, if a scratch exists on the optical disk 101, for example, a drop will appear corresponding to the scratch.
  • the stripe detection section 105 generates a stripe detection signal in accordance with changes in the signal level of the RF signal.
  • FIG. 4(b) shows the waveform of a stripe detection signal.
  • the stripe detection section 105 outputs a stripe detection signal which maintains a high level.
  • the level L is an average value of the signal level of the RF signal which is obtained by radiating laser light onto the management information area 203 or the data area 201, and is calculated based on the level of the RF signal which has hitherto been acquired by the stripe detection section 105.
  • the RF signal becomes equal to or less than the level L at time to, and it still remains equal to or less than the level L at time t1, after the lapse of the period A.
  • the level of the RF signal becomes equal to or greater than L at time t2. Therefore, from time t1 till t2, the stripe detection section 105 outputs a stripe detection signal which is at a high level.
  • the optical disk apparatus 10 determines whether the irradiated position of laser light is within the BCA 202 or not based on the frequency with which the RF signal drops. The principles thereof are as follows.
  • the stripe detection section 105 generates a stripe detection signal which takes the high level once in one rotation cycle.
  • FIG. 4(c1) shows the waveform of a stripe detection signal which takes the high level once in one rotation cycle. If the stripe detection section 105 outputs a stripe detection signal (pulse signal) which is at the high level, the multivibrator 106 receives this output, and outputs a BCA detection signal which takes a high level only during a period B.
  • FIG. 4(d1) shows the waveform of a BCA detection signal which takes a high level only during the period B. Note that the multivibrator 106 may calculate the period B from a leading edge or a trailing edge of the stripe detection signal which is at the high level.
  • the area determination section 107 Upon receiving the BCA detection signal, the area determination section 107 makes a comparison as to whether the period (detected period X) for which the high level of the BCA detection signal continues in one rotation cycle is longer than the reference period C or not.
  • the area determination section 107 determines that the current irradiated position of laser light is not at the BCA 202.
  • the microcomputer 109 instructs the transportation mechanism 108 to move the position of the optical pickup 104 by a certain distance to a position which is closer to the inner periphery of the optical disk 101. This distance is equal to less than the minimum width of the BCA 202 as defined under the specifications, for example. Then, again based on an output of the RF signal, it is determined whether the irradiated position of laser light is within the BCA 202 or not.
  • FIG. 4(c2) shows the waveform of a stripe detection signal which takes the high level a plurality of times in one rotation cycle.
  • a BCA detection signal is output which takes the high level for the period B from that point in time.
  • FIG. 4(d2) shows the waveform of a BCA detection signal whose high level period continuously continues longer than the period B.
  • the stripe detection section 105 outputs a stripe detection signal with an interval which is shorter than the period B. This is based on the fact that the stripes are disposed with an interval which is N times the channel bit length (N: 1, 2, 3 or 4).
  • the multivibrator 106 outputs a BCA detection signal whose high-level continuing period continues longer than the period B.
  • the area determination section 107 Upon receiving the BCA detection signal shown in FIG. 4(d2), the area determination section 107 makes a comparison as to whether the period (detected period X) for which the high level of the BCA detection signal continues after the lapse of one rotation cycle is longer than the reference period C or not. In the example shown in FIG. 4(e2), the detected period X is longer than the reference period C. When this comparison result is obtained, the area determination section 107 determines that the current irradiated position of laser light is within the BCA 202. Then, identification information is acquired based on the stripes which are provided in the BCA 202. The identification information can be determined based on the waveform of the stripe detection signal shown in FIG. 4(c2).
  • the area determination section 107 does not need to await the lapse of one rotation cycle before performing the above comparison. For example, even before the lapse of one rotation cycle, it may be determined that the laser light-irradiated position is within the BCA when the high level detected period of the BCA detection signal has become equal to or greater than C. Since it is not necessary to await the lapse of one rotation cycle, the time until the result of determination is obtained can be reduced.
  • FIG. 5 shows the procedure of a reading process for identification information which is performed in the optical disk apparatus 10.
  • the optical pickup 104 radiates laser to a position which is toward the outer periphery from the BCA 202, and at step S12, the optical pickup 104 receives the reflected light and generates an RF signal.
  • the stripe detection section 105 calculates an average level L of the RF signal.
  • the stripe detection section 105 determines whether the level-dropping period of the RF signal is longer than the period A or not. If longer, control proceeds to step S14; if shorter, control proceeds to step S15.
  • the stripe detection section 105 outputs a stripe detection signal which is at the high level, and control proceeds to step S16.
  • the multivibrator 106 receives the stripe detection signal which is at the high level, and outputs a BCA detection signal whose high level continues for the period B from then on. Thereafter, the process proceeds to step S18.
  • step S15 the stripe detection section 105 outputs a stripe detection signal which is at a low level
  • control proceeds to step S17.
  • step S17 the multivibrator 106 outputs a BCA detection signal which is at a low level.
  • the multivibrator 106 continues to output the BCA detection signal which is at the high level. Thereafter, the process proceeds to step S18.
  • step S18 the microcomputer 109 determines whether one rotation cycle has elapsed or not. If it has not elapsed, the process returns to step S12 and the hitherto process is repeated until one rotation cycle elapses. If it has elapsed, the process proceeds to step S19.
  • the area determination section 107 determines whether the high-level continuing time X of the BCA detection signal is longer than the reference period C or not. If shorter, control proceeds to step S20; if longer, control proceeds to step S21.
  • the area determination section 107 determines that the current laser-irradiated position is not at the BCA.
  • the microcomputer 109 instructs the transportation mechanism 108 to move the optical pickup 104, thus moving the irradiated position of light by a certain distance toward the inner periphery. Thereafter, the process returns to step S12, and the aforementioned process is continued until the current laser-irradiated position is determined to be at the BCA 202.
  • step S21 the area determination section 107 determines that the current laser-irradiated position is within the BCA 202. Then control proceeds to step S23, and from the determined BCA 202, the microcomputer 109 acquires identification information which is represented by the stripes.
  • the determination process of the optical disk apparatus 10 is completed.
  • the aforementioned process is effective also in the case where some of the stripes fail to be detected due to a recording error, for example. The reason thereof will be described with reference to FIGS. 6(a) to (d) below.
  • FIG. 6(a) shows the waveform of an RF signal whose level drop is shorter than the period A. This waveform may occur in the case where the stripes do not possess a sufficient width along the circumferential direction (in case of a recording error).
  • FIG. 6 (a) shows the waveform of the stripe detection signal. It can be seen that the stripe detection signal is at the low level.
  • FIG. 6(c) shows the overall waveform of the stripe detection signal. It is assumed that, corresponding to stripes, high-level stripe detection signals are obtained at time t11 and time t13. It is assumed that a high-level stripe detection signal that corresponds to an undetected stripe would otherwise have been obtained at time t12. Time t12 is a point in time which falls after time t11 and before time t13.
  • FIG. 6(d) shows the waveform of a BCA detection signal.
  • the multivibrator 106 Based on the high-level stripe detection signal which was output before time t11, the multivibrator 106 has already begun outputting a BCA detection signal which is at the high level.
  • the multivibrator 106 extends outputting of the high-level BCA detection signal at time t11, so that the high level is retained also at time t12.
  • the span from time t11 to time t12 is always shorter than the high-level retaining period B of the multivibrator 106.
  • the span from time t11 to time t13 is shorter than the high-level retaining period B of the multivibrator 106. This is because the stripes are periodically recorded at a predetermined interval.
  • a commonly-used optical disk apparatus will decode identification information after moving the irradiated position of laser light to within the BCA 202. Since it is common practice to perform an error correction at the time of decoding, there is already provided a function of avoiding misdetection of stripes. However, the performance of the entire reading process can be improved by further utilizing the determination process of the BCA 202 according to the present embodiment.
  • the present embodiment it is determined whether the irradiated position of laser light is within the BCA 202 or not, through a method different from that of Embodiment 1. In the present embodiment, no retriggerable one-shot multivibrator is used.
  • FIG. 7 shows the arrangement of functional blocks of an optical disk apparatus 20 according to the present embodiment.
  • the optical disk apparatus 20 includes a motor 102, an optical pickup 104, an optical pickup transportation mechanism 108, and an optical disk controller 120.
  • the optical disk controller 120 includes a revolutions control section 103, a low period detection section 125, a stripe determination section 126, an area determination section 127, and a microcomputer 128.
  • the various component elements shown in FIG. 7 the component elements which are identical in function and structure to those of the optical disk apparatus 10 according to Embodiment 1 will be denoted by like numerals, and their descriptions will be omitted.
  • the low period detection section 125 detects low periods of an RF signal.
  • the period D is a period of time which is an M times aliquot of one rotation cycle of the optical disk 101 (where M is a positive integer).
  • the stripe determination section 126 compares between the longest low period and a specific period E, and determines that a stripe exists if the longest low period is equal to or greater than the reference period E, and determines that no stripe exists if the longest low period is less than the reference period E. In accordance with the result of determination, it outputs a pulse signal (BCA detection signal). If a stripe exists, the BCA detection signal maintains a high level during that period D; if no stripe exists, the BCA detection signal maintains a low level during that period D.
  • the low period detection section 125 detects low periods, whereas the stripe determination section 126 performs determination of the longest low period, comparison against the reference period E, and outputting of a BCA detection signal.
  • the low period detection section 125 may perform determination of the longest low period, in addition to detection of low periods.
  • the stripe determination section 126 is in charge of comparison between the longest low period and the reference period E, and outputting of a BCA detection signal.
  • the low period detection section 125 may perform determination of the longest low period and comparison between the longest low period and the reference period E, in addition to detection of low periods. Then, if the longest low period is equal to or greater than the reference period E, the low period detection section 125 outputs a detection signal indicating the fact.
  • the stripe determination section 126 will output a BCA detection signal every time receiving this output.
  • the area determination section 127 determines whether the irradiated position of laser light is within the BCA 202 or not. Specifically, if the high-level continuing period of the BCA detection signal is equal to or greater than the reference period F, the area determination section 127 determines that the irradiated position of laser light is within the BCA 202. On the other hand, if the high-level continuing period of the BCA detection signal is less than the reference period F, it is determined that the irradiated position of laser light is outside the BCA 202.
  • FIG. 8(a) shows the waveform of an RF signal which is output from the optical pickup 104.
  • the low period detection section 125 measures the longest period since the RF signal has become equal to or less than a level L.
  • the level L is an average value of the RF signal which is obtained by radiating laser light onto the management information area 203 or the data area 201 of the optical disk 101.
  • the low period detection section 125 only retains the longest period up to that point, and updates the retained value when any longer period has been measured. By repeating this update process by the unit of the period D, the longest low period is determined for each period D.
  • the RF signal has a waveform such that the low period is relatively long in portions corresponding to the stripes.
  • FIG. 8(a) shows low periods in a plurality of places corresponding to the stripes. It is considered that one of these gives the longest low period during each period D.
  • the longest low period in the waveform of the RF signal appears relatively short.
  • the stripe determination section 126 compares between the longest low period and the reference period E, and determines which one of these periods is longer.
  • FIG. 8(b) shows a result of comparison between the longest low period and the reference period E.
  • the reference period E is equal to or less than the low level period where the average level of the RF signal as defined under the specifications is regarded as L; and, in the case where no waveform corresponding to a stripe as defined under the specifications exists in the RF signal, the reference period E is longer than the low level period where the average level of the RF signal as defined under the specifications is regarded as L.
  • the stripe determination section 126 In each period D, the stripe determination section 126 outputs a high-level BCA detection signal when the longest low period is equal to or greater than the reference period E, and outputs a low-level BCA detection signal when the longest low period is less than the reference period E.
  • FIG. 8(c) shows a partial waveform of the BCA detection signal.
  • FIG. 8(d) shows a waveform BCA detection signal over a longer period of time.
  • the area determination section 127 compares between the high-level continuing period of the BCA detection signal and the reference period F. Then, if the high-level continuing period is longer, it is determined that the irradiated position of laser light is within the BCA 202. If the high-level continuing period is shorter, it is determined that the irradiated position of laser light is not within the BCA 202.
  • the area determination section 127 does not need to await the lapse of one rotation cycle before performing the above comparison. For example, even before the lapse of one rotation cycle, it may be determined that the laser light-irradiated position is within the BCA when the high level detected period of the BCA detection signal has become equal to or greater than F. Since it is not necessary to await the lapse of one rotation cycle, the time until the result of determination is obtained can be reduced.
  • the low period of one stripe fails to be equal to or greater than E due to a recording error
  • the low period of another stripe within the same period D will be adopted as the longest low period, and so long as this period becomes equal to or greater than E, a BCA detection signal will be output without fail. Therefore, even if some of the stripes fail to be detected, it can be properly determined whether the laser light-irradiated position is within the BCA or not.
  • Embodiments 1 and 2 above the determination process of the BCA 202 has been described on the assumption that the optical disk 101 is a DVD-RAM.
  • DVD-Rs/-RWs, etc. which are already widely known, also have an area which is equivalent to a BCA.
  • the area is called a narrow burst cutting area (NBCA).
  • BCA and NBCA are similar in terms of the fact that stripes are provided with a predetermined interval (period). Therefore, the process which has been described in Embodiments 1 and 2 can be applied in a quite similar manner.
  • FIG. 9(a) shows the waveform of a stripe detection signal which is output corresponding to a BCA.
  • FIG. 9(b) shows the waveform of a stripe detection signal which is output corresponding to an NBCA. It will be understood that quite the same waveform is obtained also for an NBCA. Note that, since the data value logic is reversed between BCA and NBCA, the bits of the resultant data values are inverted.
  • the optical disk apparatus 10 Since BCA and NBCA are defined under different specifications, they are provided at different radial positions on the optical disk. Therefore, in Embodiment 1, for example, the "position near the BCA but toward the outer periphery" may be read as the "position near the NBCA but toward the outer periphery", and its position may be determined according to the specifications; thus, the operation of the optical disk apparatus 10 will otherwise be the same. The same will also be true for the optical disk apparatus 20 of Embodiment 2 described above.
  • BCA and NBCA may be processed in a stripe-form that has main information or management information recorded therein, whereby such an area can be determined by utilizing the procedures of Embodiments 1 and 2.
  • a DVD-ROM having a BCA would also be applicable.
  • the optical disk apparatus 20 may be a read-only DVD player.
  • the above-described process of the present invention is applicable also to Blu-ray discs or HD-DVDs for which recording and playing back of information is performed by utilizing a blue-violet semiconductor laser light, so long as a BCA is provided.
  • a stripe detection signal which is at the high level is output in reference to the average level L of the RF signal.
  • the beginning and end of a low period are measured in reference to the average level L of the RF signal.
  • other levels may also be used as references.
  • a stripe detection signal can be generated by using a different reference level.
  • FIG. 10(a) shows a relationship between a level S, which is lower than the average level L, and an RF signal.
  • the level S is set so as to be lower than the designed minimum level of an RF signal which appears when main information or management information is read, and yet higher than the designed minimum level of an RF signal corresponding to a stripe.
  • the stripe detection section 105 shown in FIG. 2 outputs a high-level stripe detection signal while the level of the RF signal is equal to less than S.
  • FIG. 10 (b) shows the waveform of a stripe detection signal which is output from the stripe detection section 105 while the level of the RF signal is equal to less than S.
  • the average level L of the RF signal is determined in a relative manner based on the RF signal which is acquired upon each read, whereas the aforementioned level S is predetermined as a fixed value.
  • the average level L and the level S may be switched between one another, depending on the situation.
  • optical disk apparatuses traditionally perform a process for detecting a scratch or the like on an optical disk. In doing so, the aforementioned level S may be utilized to detect scratches.
  • Embodiment 1 each time a stripe detection signal which is at the high level is received, the multivibrator 106 outputs a BCA detection signal whose high level continues for the period B, being triggered by that signal. Now, it will be described why it is more preferable that the period B has a length of time which corresponds to at least four times as large as the channel bit length of the BCA 202.
  • the BCA detection signal is not likely to exhibit any influence so long as the two adjoining stripes, i.e., one before and one after that stripe, are properly detected.
  • the period B is equal to or greater than at least four times the channel bit length of the BCA signal, a failure in stripe detection will not exhibit any influence, thus being able to output a BCA detection signal which is more stably accurate.
  • the BCA detection signal does not take the low level at the point in time when that stripe would have been detected.
  • a period D is defined as an M times aliquot of one rotation cycle of the optical disk 101 (where M is a positive integer), and the low period detection section 125 detects low periods of the RF signal during this period D.
  • this period D also preferably has a length of time which corresponds to at least four times or more of the channel bit length of the BCA 202.
  • the period D is set to be equal to or greater than at least four times the channel bit length of the BCA signal, a failure in stripe detection will not exhibit any influence, thus being able to output a BCA detection signal which is more stably accurate. This is the same reason as that described concerning the period B. Thus, so long as at least one of the two stripes adjoining a given stripe is detected, the BCA detection signal will never take the low level.
  • each period may elapse before reaching the next stripe of an undetected stripe, thus allowing the BCA detection signal to take the low level. Therefore, it may not be possible to output a stably accurate BCA detection signal.
  • a period A for a DVD-ROM may be as follows: for a rotation speed of 1440 rpm, the stripes are 3.00 ⁇ 1.50 ⁇ s; the period A in this case is less than 1.50 ⁇ s.
  • An optical disk playback apparatus is equipped with a method of stripe detection which utilizes the periodicity of stripes in an area of additional information. As a result, without providing a switch for position detection, it is possible to determine with a high precision whether a laser light-irradiated position is positioned within the area of additional information or not. This is useful for an apparatus which reads information that is added by processing into stripe-form a portion of a position at which main information is recorded.

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  • Optical Recording Or Reproduction (AREA)
EP05741612A 2004-06-09 2005-05-19 Optisches plattengerät und verfahren Not-in-force EP1752972B1 (de)

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DE602005022703D1 (de) 2010-09-16
CN1965354B (zh) 2011-03-30
JPWO2005122150A1 (ja) 2008-04-10
JP4490967B2 (ja) 2010-06-30
US20080002547A1 (en) 2008-01-03
EP1752972A4 (de) 2009-03-04
EP1752972B1 (de) 2010-08-04
US7995426B2 (en) 2011-08-09
CN1965354A (zh) 2007-05-16

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